Department of Primatology

Research

In recent years, I have developed an extensive approach to some of the questions I have been working on for decades to broaden our understanding of the breadth of the cultural diversity in wild chimpanzees, and in deepening our understanding of the technical intelligence skills in humans and chimpanzees. To be able to move forward on these important questions, I have been specifically working on the following areas:

1 – Cultural diversity in chimpanzees

The large “PanAfrican Chimpanzee Program” focuses on studying chimpanzee culture from all four Pan troglodytes subspecies from over 38 temporary research sites across Africa (http://panafrican.eva.mpg.de) . The program takes a holistic approach to studying chimpanzee culture and combines modern approaches like video camera traps and samples for genetic, pathogen and isotope analysis with traditional field approaches such as transects, phenology and habitat structure. The data generated by the project will have broad implications for the conservation of African primates and other sympatric species, as well as understanding the population history of chimpanzees and the factors currently affecting their distribution and survival.

Thanks to the extended video library we accumulated in the PanAfrican chimpanzee program, I have been able to analyze in detail different technical solutions adopted by different chimpanzee populations when fishing for termites from underground or aboveground nests. The technical constraints of termite fishing is limited so that individuals have the possibility to select different materials, body position and grips to fish for termites according to different nest structures. This opens the way to distinguish alternative strategies and see how much they are either due to ecological factors, or culturally based. We uncovered an impressively large number of different solutions in the populations, which emphasizes that we are still greatly underestimating behavioral and cultural diversity in chimpanzees.

2 – Technical intelligence in humans and chimpanzees

An Aka mother cracking a Panda nut within the forest with her wooden hammer and an axe as anvil while her baby is looking over her shoulder at what she is doing.

Many studies comparing humans with chimpanzees are weakened by important differences in the way the two species are compared, mainly because the chimpanzees are too often living in captivity under unnatural conditions. Since it often very difficult to ascertain which of the many differences are responsible for any differences observed, we are too often left wondering what one can conclude from such studies. In an attempt to overcome such biases I initiated several comparative studies.

In a first study on technology use, I followed the Mbendjele and Aka forest hunter-gatherers in the forest of the Central African Republic and the Republic of Congo, as they cracked open nuts of the same or very similar species as I studied in the Taï chimpanzees. This allowed us for the first time to directly compare humans and chimpanzees naturally performing a very similar technique, avoiding thereby the artificiality and arbitrariness of many comparative studies. In the first analysis, I compared the adult female techniques of the three groups (Boesch et al. in press) and could see that women, thanks to their human specific tools, could gain access to nuts that the chimpanzees cannot exploit. On the other hand, for the same type of nuts, chimpanzees proved surprisingly efficient and were by some measures more efficient that humans. This shows clearly that chimpanzee possess some high level of technical intelligence and can solve technical problems in ways similar and complementary to those of humans.

In a second study, we will be looking at the acquisition of the nut-cracking skills in youngsters by comparing the Mbendjele people with the Taï chimpanzees and compare maternal interventions in the learning process of the youngster and if they contribute to make the learning more efficient and more rapid. In both species, it takes many years to reach adult proficiency and this lengthy learning process should allow us to uncover more of the development of this technique.

In collaboration with Karline Janmaat and Haneul Jang we are evaluating the spatial skills of the Mbendjele people as they forage for fruits, tubers, nuts and honey in the forest and will compare with very similar methods to our studies of the spatial skills in Taï chimpanzees. Thus in two different cognitive domains, are we going to be able to compare the two species in a natural context.

3 – Tool use in wild chimpanzees

Tool use has been a key benchmark for humanity and therefore study of tool use in animals is of special relevance. In recent years, my efforts have been encompassed three different directions:

Document new tool use types: Using the important video material we collected on 38 different and new chimpanzee populations in the context of the “Pan African Chimpanzee Program”, we have come upon totally unknown tool use behavior that we were able to describe in some details. The first was stone throwing and accumulation that we discovered in some West African chimpanzee populations (Kühl et al. 2016), whereby they throw stones at tree trunks during their pant-hoot display and in some cases this results in the accumulation of stones within the tree trunk. The second was algae fishing with long sticks from deep in the water of small rivers that we discovered in chimpanzees from Guinea (Boesch et al. 2016).

Follow the learning skills: With two projects are we going to address the question of maternal interventions in the learning of tool use in chimpanzees. First, Katie Corogenes is focusing on nut cracking by detailing all the interactions between mothers and infants from video recordings done over three seasons. Second, Vittoria Estienne is analysing data collected with video-traps from the unhabituated chimpanzees of Loango National Park in Gabon to see how much mothers actively or passively influence the learning by offspring. Both projects will provide insights into the interaction between teaching and learning in chimpanzees.

Documenting tool-use complexity: Nut-cracking has been proposed to be one of the most complex forms of tool use in animals, and with Giulia Sirianni, we have been documenting very precisely how chimpanzees select and use their tools in the forest. Although potential hammers are over-abundant in the forest, chimpanzees optimally select their hammers by responding conditionally to the situation by considering five different physical properties (Sirianni et al. 2015). Such complex tool selection was not found in capuchin monkeys (Visalberghi et al. 2016). The extraction of honey from underground hives in Loango chimpanzees in Gabon also revealed a surprising flexibility and complexity that seemed unsurpassed when comparing with all other tool use known in chimpanzees (Estienne et al. 2016, in revision).

4 – Conservation and Conservation Biology

When working in Taï national park, I realized directly how the forest has become an island within a large cocoa and coffee plantation and that the forest would disappear without actions to promote its protection. Because of the need to have an NGO active in West Africa and specifically aimed at helping the chimpanzees, I created the wild chimpanzee foundation. Please visit www.wildchimps.org to see in detail what we are doing to help.

At the same time, too often conservation is done without the knowledge of animal population abundance and the impact of conservation measures. Presently, we are trying to develop a new method based on camera-traps to follow more precisely population trends in large mammals, including chimpanzees, My student, Noémie Cappelle, is for one year collecting very precise data in the Taï National Park to provide the necessary information for a robust and precise method that will allow then to guide our conservation activities.

Large populations are becoming rarer to find and so we are faced with the challenge of assessing the feasibility of conservation projects targeting fragmented populations. In Guinea, chimpanzees are still quite frequent but often in very fragmented populations. Is it possible to protect them? When yes, what type of fragments and actions should we perform. My student, Marie-Lyne Despres-Einspenner, is going to look into these questions.